Method for manufacturing a golf product

ABSTRACT

A process for reaction injection molding a polyurethane material for a layer of a golf ball is disclosed herein. The layer is preferably a cover for the golf ball. The process discloses preferred pressure parameters and mass flow parameters for reaction injection molding the layer. Such preferred pressure parameters include the difference from mix-head open to the shot mid-point, ΔΔPom, and the pressure difference from mix-head open to close, or ΔΔPoc. The mass flow parameters include the percentage change in mass flow ratio from mix-head open to shot mid-point, or % MFRom, and the change in mass flow ratio from mix-head open to shot mid-point, or ΔMFRom.

CROSS REFERENCES TO RELATED APPLICATIONS

Not Applicable

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not Applicable

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a process for manufacturing a layer ofa golf ball. More specifically, the present invention relates to aprocess for reaction injection molding a layer of a golf ball.

2. Description of the Related Art

Reaction injection molding (“RIM”) is a process used to make golf ballcomponents, such as one-piece balls, covers, cores, and inner layers.Highly reactive liquids are injected into a closed mold, mixed usuallyby impingement and/or mechanical mixing in an in-line device such as a“peanut mixer”, and polymerized primarily in the mold to form acoherent, molded article. When used to make a thermoset polyurethane orpolyurea component, RIM usually involves a rapid reaction between twotypes of reactants: (a) a polyol or other material with an activehydrogen, such as a polyfunctional alcohol or amine (hereinafterreferred to as “polyol” or “POLY”); and (b) an isocyanate-containingcompound (hereinafter referred to as “isocyanate” or “ISO”). Thereactants are stored in separate tanks prior to molding and maybe firstmixed in a mix-head upstream of a mold and then injected into the mold.The liquid streams are metered in the desired weight to weight ratio andfed into an impingement mix-head, with mixing occurring under highpressure, e.g., 1500 to 3000 pounds per square inch (“psi”). The liquidstreams impinge upon each other in the mixing chamber of the mix-headand the mixture is injected into the mold. One of the liquid streamstypically contains a catalyst for the reaction. The reactants reactrapidly after mixing to gel and form polyurethane or polyurea polymers.

RIM offers several advantages over conventional, injection andcompression molding techniques for producing golf products and/orequipment. For example, in the RIM process, the reactants aresimultaneously mixed and injected into the mold, forming the desiredcomponent. In conventional techniques, the reactants must first be mixedin a mixer separate from the molding apparatus, then added into theapparatus. In such a process, the mixed reactants first solidify andmust later be melted in order to properly mold the desired components,etc.

Additionally, the RIM process requires lower temperatures and pressuresduring molding than injection or compression molding. Under the RIMprocess, the molding temperature is maintained from about 90 to about180° F., and usually at about 100–160° F., in order to ensure properinjection viscosity. Compression molding is typically completed at ahigher molding temperature of about 320° F. (160° C.) while injectionmolding is completed at an even higher temperature range of 392–482° F.(200–250° C.). Molding at a lower temperature is beneficial when, forexample, the cover is molded over a very soft core so that the very softcore does not melt or decompose during the molding process.

Moreover, the RIM process creates more favorable durability propertiesin a golf ball component than conventional techniques. For example, agolf ball cover produced by a RIM process has a uniform or “seamless”cover in which the properties of the cover material in the region alongthe parting line are generally the same as the properties of the covermaterial at other locations on the cover, including at the poles. Theimprovement in durability is due to the fact that the reaction mixtureis distributed uniformly into a closed mold. This uniform distributionof the injected materials reduces or eliminates knit-lines and othermolding deficiencies which can be caused by temperature differencesand/or reaction differences in the injected materials. The RIM processresults in generally uniform molecular structure, density and stressdistribution as compared to conventional injection molding processes,where failure along the parting line or seam of the mold can occurbecause the interfacial region is intrinsically different from theremainder of the cover layer and, thus, can be weaker or more stressed.

Furthermore, the RIM process is relatively faster than conventionaltechniques. In the RIM process, the chemical reaction usually takesplace in under 5 minutes, typically in less than two minutes, sometimesin under one minute and, in many cases, in about 30 seconds or less. Thedemolding time may be 10 minutes or less. The molding process for theconventional methods itself typically takes about 15 minutes. Thus, theoverall speed of the RIM process makes it advantageous over theinjection and compression molding methods.

Several patents disclose the use of RIM utilized for golf balls. One ofthe earliest disclosures of RIM is U.S. Pat. No. 5,356,941 to Sullivanet al., for Game Balls having Improved Core Compositions, whichdiscloses the use of RIM.

Further discloses are set forth in U.S. Pat. No. 6,803,119 to Sullivanet al., for a Multi-Layer Golf Ball, and U.S. Pat. No. 6,287,217 toSullivan et al., for Multi-Layer Golf Ball, both which disclose the useof a BAYFLEX RIM polyurethane as a cover for a golf ball.

A further disclosure is set forth in U.S. Pat. No. 6,290,614 to KennedyIII et al., for a Golf Ball Which IncludesFast-Chemical-Reaction-Produced Component And Method Of Making Same,which discloses a RIM process in which the temperature is 90–180° F.,and the pressure is 200 pounds per square inch (“psi”) or less, and theprocessing time is 10 minutes or less, and preferably 30 second or less.This patent further discloses that the mix head pressure is between 1500to 3000 psi.

A further disclosure is set forth in U.S. Pat. No. 6,533,566 to Tzivaniset al., for an Apparatus For Making A Golf Ball, which discloses aturbulence inducing mold for a RIM process.

A further disclosure is set forth in U.S. Pat. No. 6,290,614 to KennedyII et al., for a Multi-Layer Golf Ball, which discloses a RIM systemutilized for a cover of a golf ball.

Another disclosure is U.S. Pat. No. 6,309,313 to Peter, for a Low Cost,Resilient, Shear Resistant Polyurethane Elastomers For Golf Ball Covers,which discloses using RIM at temperatures of 120–250° F.

Yet a further disclosure is set forth in U.S. Pat. No. 6,645,088 to Wuet al., for Reaction Injection Moldable Compositions, Methods For MakingSame, And Resultant Golf Articles, which discloses the use of a materialwith a viscosity less than 20,000 cPs, and an injection pressure lessthan 2500 psi.

Yet a further disclosure is set forth in U.S. Pat. No. 6,663,508 toKeller et al., for Multi-Layer Golf Ball With Reaction Injection MoldedPolyurethane Component, which discloses the use of a BAYFLEX MP-10,000RIM system which operates at 10–5 mmHg at 77° F. and has a molecularweight of 600–700.

Yet a further disclosure is set forth in U.S. Pat. No. 6,685,579 toSullivan, for Multi-Layer Cover Polyurethane Golf Bal, which disclosesthe use of a RIM with a material having a viscosity up to 200 cPs andpressures of 2000 to 2500 psi.

Yet a further disclosure is set forth in U.S. Pat. No. 6,716,954 toKeller et al., for a Golf Ball Formed From A Polyisocyanate CopolymerAnd Method Of Making Same, which discloses the use of DESMODUR HLmaterial which has a NCO content of 10–11%.

A further disclosure is set forth in U.S. Pat. No. 6,755,634 to Tzivaniset al., for an Apparatus For Forming A Golf Ball With Deep Dimples,which discloses an apparatus capable of using RIM at temperatures of50–250° F., pressures of 100 psi or less, and an impingement pressure of150–195 bars.

A further disclosure is set forth in U.S. Pat. No. 6,787,091 to Daltonet al., for a Reaction Injection And Compression Molding Of A Golf Ball,which discloses a reaction injection compression molding RCIM processwhich operates at an impingement head pressure of 1000 to 5000 psi.

Another disclosure is U.S. Patent Publication Number 2002/0016435 toSimonutti et al., for a Method OF Making A Golf Ball Product FromFast-Curing Reaction Injection Molded Polyurethane, which discloses aRIM process with an isocyanate temperature of 100–130° F., a polyoltemperature of 100–130° F., a raw material tank pressure of 40–80 psi,an isocyanate pressure of 1000–3000 psi, polyol pressure of 1000–3000,mold temperature of 130–200° F., and an inject time of less ten seconds.

The term “demold time” generally refers to the mold release time, whichis the time span from the mixing of the components until the earliestpossible time at which the part may be removed from the mold. At thattime of removal, the part is said to exhibit sufficient “greenstrength.” The term “reaction time” generally refers to the setting timeor curing time, which is the time span from the beginning of mixinguntil the time at which the product no longer flows. Further descriptionof the terms setting time and mold release time are provided in the“Polyurethane Handbook,” edited by Gunter Oertel, Second Edition, ISBN1–56990-157-0, herein incorporated by reference in its entirety.

Although RIM has been widely used to mold large parts, it has onlyrecently begun to be used in molding small parts, such as golf balls andgolf ball components. One challenge is the relatively small shot sizeassociated with such small parts. The small shot size demands thatprecise amounts of the two reactants be mixed thoroughly andconsistently throughout the shot, When the amount of either reactantchanges or the degree of mixing changes, the rate at which the part'shardness develops will also change and the final part hardness may beundesirable. These inferior material properties can affect, for example,a golfball's susceptibility to damage when removing the ball from themold and the toughness of a finished golf ball in resisting scuff damagewhen struck by a golf club.

Another challenge is ensuring consistency in the finished product overseveral shot operations. Because the shot size is so small, even smallchanges in conditions affecting either the reactants or the RIM processitself can change the quality of the finished product.

Although quality control techniques are known, they are especiallydifficult to apply to golf ball components. For example, at the demoldtime, it is difficult to determine the quality of a RIM-produced golfball; the earliest time when the quality can be determined isapproximately 1 hour after demolding. Even then, test results may change12 to 24 hours later as the RIM material continues to cure. Destructivetesting destroys the ball and entails extra costs which must be passedon to the consumer. Balls where the mixing was poor or the mix ratio wasincorrect may look and feel identical to balls with acceptable quality.As a result of the extra time incurred in detecting defective balls, alarge run of unacceptable golf balls may be produced. Hence, new methodsfor controlling the RIM manufacturing of golf products, such as golfballs and/or components thereof, are desired.

BRIEF SUMMARY OF THE INVENTION

One aspect of the present invention is a process for reaction injectionmolding a layer of a golf ball. The process may be defined by componentReynold's numbers through the mixhead, impingement velocities throughthe mixhead, pressure changes of components within a shot, overallpressure difference between components, pressure delta delta, and mixratio delta.

Another aspect of the present invention is a process for reactioninjection molding a layer for a golf ball. The process begins withintroducing a polyol component and an isocyanate component into amolding apparatus. Next, the polyol component and the isocyanatecomponent react within the molding apparatus to create a reactionproduct. Next, a layer for a golf ball is formed from the reactionproduct. An impingement velocity for the isocyanate component rangesfrom 50 to 2,000 feet per second, and an impingement velocity for thepolyol component ranges from 50 to 2,000 feet per second.

Yet another aspect of the present invention is a process for reactioninjection molding a layer for a golfball, wherein a pressure differenceΔΔPom is less than 200 psi and a change in mix ratio, % MFRom, frommix-head open to shot mid-point is within 20%. The process begins withintroducing a polyol component and an isocyanate component into amolding apparatus. Next, a layer for a golf ball is formed from thereaction product of the polyol component and the isocyanate component.

Having briefly described the present invention, the above and furtherobjects, features and advantages thereof will be recognized by thoseskilled in the pertinent art from the following detailed description ofthe invention when taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 shows a general RIM process flow diagram.

FIG. 2 shows a typical pressure profile over an entire RIM shot cycle.

FIG. 3 shows an enlarged view of the box 3—3 in FIG. 2.

FIG. 4 shows a second pressure profile of the shot portion of a shotcycle.

FIG. 5 shows a third pressure profile of the shot portion of a shotcycle.

FIG. 6 shows a first shot history of a RIM machine used to make golfballs over 24 hours.

FIG. 7 shows the same shot history as FIG. 6, analyzed differently.

FIG. 8 shows a second shot history of a RIM machine used to make golfballs over 24 hours.

FIG. 9 shows a third shot history of a RIM machine used to make golfballs over 24 hours.

FIG. 10 shows a fourth shot history of a RIM machine used to make golfballs over 16 hours.

FIG. 11 shows a fifth shot history of a RIM machine used to make golfballs over 24 hours.

FIG. 12 shows a sixth shot history of a RIM machine used to make golfballs over 24 hours.

FIG. 13 shows a seventh shot history of a RIM machine used to make golfballs over 24 hours where the measured parameter is the change in massflow rate ratio, ΔMFRoc.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 shows a general process flow diagram for forming a polyurethanecover for a golfball utilizing a reaction injection molding (“RIM”)apparatus. An isocyanate component from bulk storage is fed through line80 to an isocyanate tank 100. The isocyanate component is heated to thedesired temperature, e.g., about 90 to about 180° F., by circulating itthrough heat exchanger 82 via lines 84 and 86. The isocyanate componentpreferably comprises an isocyanate and at least one additional material.

A polyol component is conveyed from bulk storage to a polyol tank 108via line 88. The polyol component is heated to the desired temperature,e.g. about 90 to about 180° F., by circulating it through heat exchanger90 via lines 92 and 94. The polyol component preferably comprises apolyol and at least one additional material. Dry nitrogen gas is fedfrom nitrogen tank 96 to isocyanate tank 100 via line 97 and to polyoltank 108 via line 98. The isocyanate component is fed from isocyanatetank 100 via line 102 through a metering cylinder or metering pump 104into mix-head inlet line 106. The polyol component is fed from polyoltank 108 via line 110 through a metering cylinder or metering pump 112into mix-head inlet line 114. The mix-head 116 receives the isocyanatecomponent and the polyol component, mixes them, and provides for them tobe fed through nozzle 118 into injection mold 120. The injection mold120 preferably has a top mold 122 and a bottom mold 124. Mold heating orcooling can be performed through lines 126 in the top mold 122 and lines140 in the bottom mold 124. The materials are preferably maintainedunder controlled conditions to insure a desired pressure profile.

Inside the mix-head 116, the isocyanate component and the polyolcomponent are directed through small orifices, or reducers, atultra-high velocity to provide excellent mixing. Additional mixing maybe conducted using an aftermixer 130, which typically is constructedinside the mold between the mix-head and the mold cavity. The reactionmixture viscosity should be sufficiently low to ensure that the emptyspace in the mold is completely filled.

Methods and apparatus such as described above are disclosed in greaterdetail in U.S. Pat. No. 6,290,614 to Kennedy III et al., for a Golf BallWhich Includes Fast-Chemical-Reaction-Produced Component And Method OfMaking Same, U.S. Pat. No. 6,533,566 to Tzivanis et al., for anApparatus For Making A Golf Ball, U.S. Pat. No. 6,663,508 to Keller etal., for Multi-Layer Golf Ball With Reaction Injection MoldedPolyurethane Component, and U.S. Pat. No. 6,755,634 to Tzivanis et al.,for an Apparatus For Forming A Golf Ball With Deep Dimples, all of whichare hereby incorporated by reference in their entireties.

FIG. 2 shows a preferred pressure profile over an entire shot cycle. Atpoint A, the machine is in recirculation mode. At point B, the machinebegins to build pressure for the shot. At point C, the machine holds atthe shot pressure. At point D, the mix-head opens to dispense the shot.Point E is the midpoint of the shot. At point F, the mix-head closes toend the shot. At point G, the machine ends the hold at shot pressure. Atpoint H, the machine is back in recirculation mode. A new shot cyclebegins. Table 1 summarizes the data shown in FIG. 2.

TABLE ONE Label Event A Recirculation Mode B Build Pressure for Shot CHold at Shot Pressure D Mix-Head Opens E Midpoint of Shot F Mix-HeadCloses G End Hold at Shot Pressure H Recirculation Mode

The pressure profile for each reactant should remain constant during theactual shot itself, which occurs from point D to point F. The startpressure, or the pressure at open, occurs at point D. The finalpressure, or the pressure at close, occurs at point F. In practice, thisusually means the pressure profile for each reactant over the entireshot cycle should be constant. Here, “constant” means the pressureprofile has the same shape, not the same value, over the shot cycle.

The start pressure for each reactant can be controlled by pressureregulators within the RIM machine. However, the final pressure iscontrolled by the temperature, viscosity, flow rate, and reducer size.Preferably, the temperature for each reactant is adjusted such that thetwo reactants have approximately the same viscosity; this allows forbetter mixing of the reactants. The flow rate is often controlledindirectly by hydraulic adjustments and is dependent on the viscosity ofthe components and the size of the orifice or reducer it must travelthrough. Reducers, which are components with one or more fixed-sizeholes located inside the mix-head, restrict the flow of the reactantsand therefore raise the pressure required to dispense each reactant at agiven flow rate. The reducer size can be changed to obtain the desiredfinal pressure; e.g., larger reducers can be installed to lower thefinal pressure. Thus, the pressure profile for each reactant (isocyanatecomponent and polyol component) is usually different due to balancingthese variables.

The RIM molding process can be monitored and controlled by acquiring andanalyzing the pressures and flow rates for each reactant and the mixratio during the actual shot. This requires that the isocyanatecomponent pressure, polyol component pressure, isocyanate component massflow, polyol component mass flow, and mass ratio be collected at thestart of the shot when the mix-head opens (point D), the mid-point ofthe shot (point E), and when the mix-head closes (point F). A preferredmixing during a shot can be determined from this data.

The pressure profile will repeat until something changes in the process;e.g. the mix-head needs cleaning, the temperature control for a reactantis drifting, . . . etc. This indicates that something has affected themix quality and therefore part quality may suffer. When this occurs,adjustments need to be made to the system to ensure restructuring of theproper RIM pressure profile.

The process is deemed “in control” and data is collected from one ormore shots to establish a baseline. The baseline data collectedcomprises datapoints indicating the value of one or more of thefollowing variables: the isocyanate pressure when the mix-head opens (atpoint D), or Poi; the isocyanate component pressure at the midpoint ofthe shot (at point E), or Pmi; the isocyanate component pressure whenthe mix-head closes (at point F), or Pci; the polyol component pressurewhen the mix-head opens (at point D), or Pop; the polyol componentpressure at the midpoint of the shot (at point E), or Pmp; the polyolcomponent pressure when the mix-head closes (at point F), or Pcp; theisocyanate component mass flow rate when the mix-head opens, or MFoi;the isocyanate component mass flow rate at the mid-point of the shot, orMFmi; the isocyanate component mass flow rate when the mix-head closes,or MFci; the polyol component mass flow rate when the mix-head opens, orMFop; the polyol component mass flow rate at the mid-point of the shot,or MFmp or the polyol component mass flow rate when the mix-head closes,or MFcp. These variables are process parameters which can be used todetermine the status of the process. Those skilled in the pertinent artwill recognize that other variables may be measured as well. Forexample, it may be desirable to measure the reactant pressure when themachine begins to build pressure for the shot (at point B) and thereactant pressure when the hold at shot pressure ends (at point G). Itmay also be desirable to measure other variables at different locationswithin the RIM machine and use those variables to control the process.

From this data, several other process parameters may be determined. Theaverage open pressure, or Poave, maybe calculated as [(Pop+Poi)/2]. Theaverage close pressure, or Pcave, may be calculated as [(Pcp+Pci)/2].The pressure difference at open, or ΔPo, may be calculated as (Pop−Poi).The pressure difference at close, or ΔPc, may be calculated as(Pcp−Pci). The change in average pressure from open to close, orΔPocave, may be calculated as (Pcave−Poave). The change in pressuredifference from mix-head open to close, or ΔΔPoc, may be calculated as(ΔPc−ΔPo) or [(Pcp−Pci)−(Pop−Poi)]. An alternative change in pressuredifference from mix-head open to the shot mid-point, or ΔΔPom, maybecalculated as (ΔPm−ΔPo) or [(Pmp−Pmi)−(Pop−Poi)].

The change in isocyanate component mass flow rate from open to close, orΔMFoci, may be calculated as (MFci−MFoi). The change in polyol componentmass flow rate from open to close, or ΔMFocp, may be calculated as(MFcp−MFop). The change in mass flow ratio from mix-head open to close,or ΔMFRoc, may be calculated as [(MFcp/MFci)−(MFop/MFoi)]. Thepercentage change in mass flow ratio from mix-head open to close, or %MFRoc,can be calculated as or ΔMFRoc/(MFop/MFoi). The change in massflow ratio from mix-head open to shot mid-point, or ΔMFRom, may becalculated as [(MFmp/MFmi)−(MFop/MFoi)]. The percentage change in massflow ratio from mix-head open to shot mid-point, or % MFRom, can becalculated as or ΔMFRom/(MFop/MFoi).

The Reynold's number through the mixhead may also be calculated from thecomponent viscosity, component density, volumetric flow rate, and thediameter of the orifice. Again, those skilled in the pertinent art willrecognize that other parameters or variables may be used. For example,the average isocyanate mass flow rate during the shot could becalculated as [(MFoi+MFci)/2]. Alternatively, known constants could beused as well. For example, with knowledge of the reducer size, one couldalso calculate the pressure of a reactant upon impingement in themixhead. The variables listed above may also be considered processparameters.

FIG. 3 is an enlarged view of the box in Δ, which shows the pressureprofile during the shot portion of the cycle. The pressure profile islabeled to show when the variables Poi, Pop, Pci, and Pcp and theprocess parameters ΔPo and ΔPc are measured. Table Two uses the pressureprofile given in Table One to calculate the values of the processparameters listed.

TABLE TWO Parameter Value (psi) ΔPo −100 ΔPc −200 ΔPocave 150 ΔΔPoc −100

FIG. 4 is a second pressure profile of the shot portion of a shot cycle.FIG. 4 differs from FIG. 3 in that ΔPo and ΔPc have the same value, sothat ΔΔPoc is zero.

FIG. 5 is a third pressure profile of the shot portion of a shot cycle.FIG. 5 differs from FIG. 3 in that ΔPo is greater than ΔPc and thepressure of both reactants decreases throughout the shot portion.

FIG. 6 shows a graph of a first shot history of a RIM machine used tomake golfballs over 24 hours. The parameter measured was ΔΔPoc

FIG. 7 shows the same shot history as FIG. 6. In FIG. 7, the shots weredivided into subgroups of six shots. This is reflected by the lowernumber of points on the graph.

FIG. 8 shows a graph of a second shot history of a RIM machine used tomake golfballs over 24 hours. The parameter measured was ΔΔPoc. Notethat the upper and lower bounds here are different from those of FIG. 6.In FIG. 8, the shots drift towards the upper bound.

FIG. 9 shows a graph of a third shot history of a RIM machine used tomake golfballs over 24 hours. The parameter measured was ΔΔPoc.

FIG. 10 shows a graph of a fourth shot history of a RIM machine used tomake golf balls over 24 hours. The parameter measured was ΔΔPoc.

FIG. 11 shows a graph of a fifth shot history of a RIM machine used tomake golf balls over 24 hours. The parameter measured was ΔΔPoc.

FIG. 12 shows a graph of a sixth shot history of a RIM machine used tomake golf balls over 24 hours. The parameter measured was ΔΔPoc. In FIG.12, routine preventive maintenance was performed on the machine atapproximately 15:00. The production runs before and after 15:00 showclear differences between their baseline central tendencies and naturalvariations. Again, the indicated upper and lower bounds are shown forthe production run prior to 15:00.

FIG. 13 shows a graph of a seventh shot history of a RIM machine used tomake golf balls over 24 hours. The parameter measured was the change inmass flow rate ratio, ΔMFRoc. The dark lines indicate the upper andlower bounds of an in-control process.

Over the course of any shot cycle (from points B to G in FIG. 2), thepressure at the end of that shot cycle for a reactant (point G) ispreferably within 100 psi of the pressure at the beginning of that shotcycle for that reactant (point B). More preferably, it is within 50 psi,and most preferably it is within 10 psi.

Over the course of any shot cycle (from points B to G in FIG. 2), thepressure of the two reactants (ISO and POLY) at the end of that shotcycle (point G) is preferably within 700 psi of each other. Morepreferably, they are within 200 psi of each other, and most preferablythey are within 100 psi of each other.

Over the course of any shot cycle (from points B to G in FIG. 2), theimpingement velocity of a reactant into the mixhead is preferably withinthe range of 8 to 5000 ft/sec. More preferably, it is within the rangeof 50 to 2000 ft/sec, and most preferably it is within the range of 100to 1000 ft/sec. Over the course of any shot cycle (from points B to G inFIG. 2), the Reynolds number of a reactant at impingement is preferablywithin the range of 1.3 to 2,500,000. More preferably, it is within therange of 3.2 to 630,000. Most preferably it is within the range of 9.5to 440,000.

From the foregoing it is believed that those skilled in the pertinentart will recognize the meritorious advancement of this invention andwill readily understand that while the present invention has beendescribed in association with a preferred embodiment thereof, and otherembodiments illustrated in the accompanying drawings, numerous changes,modifications and substitutions of equivalents may be made thereinwithout departing from the spirit and scope of this invention which isintended to be unlimited by the foregoing except as may appear in thefollowing appended claims. Therefore, the embodiments of the inventionin which an exclusive property or privilege is claimed are defined inthe following appended claims.

1. A process for reaction injection molding a layer for a golf ball, theprocess comprising: introducing a polyol component into a moldingapparatus; introducing an isocyanate component into the moldingapparatus; and forming a layer for a golf ball, the layer formed fromthe reaction product of the polyol component and the isocyanatecomponent; wherein a pressure difference ΔΔPom is less than 100 psi. 2.The process according to claim 1 wherein a pressure difference ΔΔPoc isless than 100 psi.
 3. The process according to claim 1 wherein aReynold's Number for the isocyanate component ranges from 5 to 500,000and a Reynold's Number for the polyol component ranges from 5 to500,000.
 4. The process according to claim 1 wherein an impingementvelocity for the isocyanate component ranges from 50 to 2,000 feet persecond, and an impingement velocity for the polyol component ranges from50 to 2,000 feet per second.
 5. The process according to claim 1 whereina pressure change of the polyol component during the process is lessthan 350 psi, and a pressure change of the isocyanate component duringthe process is less than 350 psi.
 6. The process according to claim 1wherein the change in mix ratio, % MFRom, from mix-head open to shotmid-point is within 10%.
 7. The process according to claim 1 wherein aReynold's Number for the isocyanate component ranges from 50 to 1,000and a Reynold's Number for the polyol component ranges from 50 to 1,000.8. The process according to claim 1 wherein an impingement velocity forthe isocyanate component ranges from 100 to 1,000 feet per second, andan impingement velocity for the polyol component ranges from 100 to1,000 feet per second.
 9. The process according to claim 1 wherein thelayer is a cover for the golf ball.
 10. A process for reaction injectionmolding a layer for a golf ball, the process comprising: introducing apolyol component into a molding apparatus; introducing an isocyanatecomponent into the molding apparatus; reacting the polyol component andthe isocyanate component within the molding apparatus to create areaction product; and forming a layer for a golf ball, the layer formedfrom the reaction product; wherein an impingement velocity for theisocyanate component ranges from 50 to 2,000 feet per second, and animpingement velocity for the polyol component ranges from 50 to 2,000feet per second; wherein the change in a mix ratio % MFRoc is within10%.
 11. A process for reaction injection molding a layer for a golfball, the process comprising: introducing a polyol component into amolding apparatus; introducing an isocyanate component into the moldingapparatus; reacting the polyol component and the isocyanate componentwithin the molding apparatus to create a reaction product; and forming alayer for a golf ball, the layer formed from the reaction product;wherein an impingement velocity for the isocyanate component ranges from50 to 2,000 feet per second, and an impingement velocity for the polyolcomponent ranges from 50 to 2,000 feet per second; wherein a pressuredifference ΔΔPoc is less than 100 psi.
 12. The process according toclaim 10 wherein a Reynold's Number for the isocyanate component rangesfrom 5 to 500,000 and a Reynold's Number for the polyol component rangesfrom 5 to 500,000.
 13. The process according to claim 10 wherein apressure change of the polyol component during the process is less than350 psi, and a pressure change of the isocyanate component during theprocess is less than 350 psi.
 14. The process according to claim 10wherein a Reynold's Number for the isocyanate component ranges from 50to 1,000 and a Reynold's Number for the polyol component ranges from 50to 1,000.
 15. The process according to claim 10 wherein an impingementvelocity for the isocyanate component ranges from 100 to 1,000 feet persecond, and an impingement velocity for the polyol component ranges from100 to 1,000 feet per second.
 16. A process for reaction injectionmolding a layer for a golf ball, the process comprising: introducing apolyol component into a molding apparatus; introducing an isocyanatecomponent into the molding apparatus; and forming a layer for a golfball, the layer formed from the reaction product of the polyol componentand the isocyanate component; wherein a pressure difference ΔΔPom isless than 200 psi and a change in mix ratio, % MFRom, from mix-head opento shot mid-point is within 20%.
 17. The process according to claim 16wherein a pressure difference ΔΔPoc is less than 200 psi.
 18. Theprocess according to claim 16 wherein a Reynold's Number for theisocyanate component ranges from 5 to 500,000 and a Reynold's Number forthe polyol component ranges from 5 to 500,000.
 19. The process accordingto claim 16 wherein an impingement velocity for the isocyanate componentranges from 50 to 2,000 feet per second, and an impingement velocity forthe polyol component ranges from 50 to 2,000 feet per second.